From an industrial point of view, the resolution of (.+-.) chiral compounds is in most cases an advantageous alternative to the asymmetric synthesis of one of the enantiomers.
In the case of compounds of formula (I), resolution through biased crystallization can be carried out by several methods when R is an aryl group (1, 2). Syntheses of compounds of formula (I) in which R is an alkyl group, from chiral reactants have also been described (3 to 11). These syntheses do not represent a general method but are specified on a case by case basis and until now, resolutions based on a diastereoisomeric crystallization or a preferential crystallization have not resulted in a satisfactory outcome (12 to 18).